Automatic control system for concrete pump



April 30, 1968 E. L. SHERROD AUTOMATIC CONTROL SYSTEM FOR CONCRETE PUMP 5 Sheets-Sheet l Filed Feb.

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I ll l I I i I I l Il l lllll|ll1|l April 30, 1968 E. SHERROD AUTOMATIC CONTROL SYSTEM FOR CONCRETE PUMP 5 Sheets-Sheet 3 Filed Feb. 3, 1966 nitecl States Pater Oce 3,389,388 Patented Apr. 30, 1968 3,380,388 AUTOMATIC CONTROL SYSTEM FOR CONCRETE PUMP Eugene L. Sherrod, Broolnield, Wis., assignor of one-half to Robert T. Sheri-d, Milwaukee, Wis. Filed Feb. 3, 1966, Ser. No. 524,675 Claims. (Cl. 10349) ABSTRACT OF THE DISCLOSURE Each of a pair of pumping cylinders has its piston driven by a double-acting hydraulic cylinder and has a front and a rear limit switch to be actuated as the piston nears the end of each of its strokes and actuation of which effects stroke termination. A pump valve is shiftable between a pair of operating positions, at each of which it communicates one pumping cylinder with a supply of material to be pumped and the other with a delivery line. Shifting of the pump valve depends upon actuation of a rear limit switch of one pump cylinder and a front limit switch of the other. Intermediate its positions the shifting pump valve actuates another limit switch that initiates a new stroke of each pump piston.

This invention relates to hydraulically actuated cylinder type pumps for freshly mixed concrete and other substantially heavy, viscous materials, and the invention is more particularly concerned with means for controlling the sequence of piston and pump valve operations in hydraulically actuated pumps for concrete and the like.

Pumps of the type here under consideration comprise two or more cylinders, each open at its front end and in each of which a piston is reciprocable; a hopper or trough containing a feed screw to propel material to be pumped into a feed chamber in front of the cylinders and from which chamber material is drawn into each cylinder during rearward charging motion of its piston; and a delivery line into which material is expelled from the cylinder during the forward discharging stroke of its piston. Such a pump must also include valve means to selectively control communication between each cylinder and the feed chamber or delivery line.

It has been the general practice to mechanically actuate the pistons of such a pump by means of a pitman connection with a rotating crankshaft or the like, which produced constantly varying rates of piston speed. This invention, however, concerns a pump the pistons of which are reciprocated by hydraulic drivers, which can move the pistons through their strokes at substantially steady rates.

While the hydraulically actuated pumps heretofore available have been generally successful in producing a substantially uniform rate of discharge from each cylinder during the time that the piston for that cylinder was actually moving in its forward stroke, they have not been capable of producing a smooth, steady discharge all through their pumping cycle, owing to the fact that there was always an interval of some duration between the time that one piston ended its discharge stroke and the time that the next piston began to move forward. That interval was occupied by movement of the valve means from one position to another.

In a pump of the character here under consideration, it is not feasible to begin movement of the valve means until the discharging piston actually reaches the end of its stroke. This is because the valve means must move through the material being pumped, and as long as a piston is moving forward, it tends to maintain under compression the column of material ahead of it, which column extends through the valve means and along the delivery line. Such compressed material strongly resists motion of the valve means.

In prior pumps there was not only a delay while the valve means moved all the way from one to another of its operating positions, but further delay after the valve means had arrived at each new position due to lag in the control mechanism of the machine and in the response of the hydraulic drivers to the control system.

These delays between successive discharging strokes, while perhaps not long in themselves, amounted to a substantial portion of the total cycle time, and their cumulative effect during an eight hour working day reduced pump capacity very substantially below what it would have been if discharge of material from the pump had been continuous rather than intermittent.

With the foregoing considerations in mind, it is the general object of the present invention to substantially decrease the interval between successive discharge strokes in a hydraulically driven pump of the character described,

thereby increasing the overall cycle speed of the pump and proportionately increasing its capacity for a given displacement.

'It is also an object of this invention to provide a very versatile and flexible electr c-hydraulic control system for a pump of the character described which provides for precise synchronization of the movements of its pistons and valving.

A further object of this invention is to provide an electro-hydraulic control system for a pump of the character described wherein each control actuation can be initiated slightly before the response thereto is required, so as to compensate for the delays and lags which normally attend the operation of such a mechanism, such for example as the time required for a hydraulic control valve to be shifted from one position to another by a solenoid actuator, and which control system is easily adjustable to compensate for variations in such response lags.

A still further object of this invention is to provide a control system of the character described for a hydraulically actuated concrete pump or the like whereby pressure fluid is directed in the most advantageous manner to the several hydraulic operators or drivers for the pump' pistons and the valve means, without being forced through relief valves, so as to achieve highly efficient utilization of the power available for operation of the machine.

In pumps of the type here referred to, the screw conveyor by which freshly mixed concrete is propelled along the feed trough to the feed chamber frequently ja'ms as a result of stones in the concrete mix becoming wedged between the edges of the conveyor screw and the bottom or sides of the feed trough. In the past, this has always necessitated manual manipulation of the controls of the control system to first stop the conveyor, then reverse the drive therefor, and finally restart the drive after the obstruction was cleared. In cases where severe jamming of the screw conveyor occurred, it was sometimes necessary to shut down the entire pump rather than have it continue to operate uselessly while the obstruction to conveyor rotation was cleared.

With this objection in mind, it is another purpose of this invention to provide the screw conveyor of a pump of the character described with a reversible motor and with control means for said motor which effects normal or forward rotation of the conveyor thereby as long as the load on the motor is more or less normal, but which control means responds to a rise in the load on the motor to a predetermined value, such as occurs when a stone in the feed trough interferes with normal rotation of the screw, to automatically effect reversal of the conveyor drive motor the slight extent necessary to dislodge the obstruction to normal rotation of the conveyor and to thereafter automatically restart the motor for normal rotation of the conveyor.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

FIGURE 1 is a longitudinal sectional view of a pump for concrete and similar materials, embodying the principles of this invention;

FIGURE 2 is a cross sectional view taken generally on the plane of the line 2-2 in FIGURE 1;

FIGURE 3 is a diagram of the hydraulic system of the pump of this invention; and

FIGURE 4 is a diagram of the electrical system of the pump.

Referring now to the accompanying drawings, and more particularly to FIGURES l and 2, the numeral 5 designates generally a pump of the general type to which this invention relates, intended for pumping freshly mixed concrete and similar heavy, viscous materials. In general, such a pump comprises a plurality of cylinders, disposed substantially horizontally at the bottom of the machine and in side-'by-side relationship. By way of illustration, the pump here illustrated is shown as having two cylinders designated by (1-41 and C2. Each of the cylinders is open at its front to a feed chamber 6 that forms a downward extension of a hopper-like feed trough 7 which overlies the cylinders. A screw 8 in the trough is rotatably driven by a hydraulic motor SM to advance material along the trough and into the feed chamber 6 so that said chamber is always full of material when the machine is in oporation.

Pistons P-ll and 19-2 are reciprocable in the cylinders C- 1 and C-2 respectively. As each piston moves rearwardly in its charging stroke, it draws material into its cylinder, through the open front of the latter, from the feed chamber 6. When the piston moves forwardly in its discharging stroke, a valve 10, which is then in register with the front of the cylinder, conducts material expelled from the cylinder through a generally S'shape'd passage 10' in the valve to a delivery line 11. Hence, the valve passage 10' in effect forms a part of the delivery line, and because of the shape of this passage, the valve 10 can be conveniently referred to as an S valve.

The inlet 11' of the delivery line is so located with respect to the cylinders that its axis and their axes define the points of an isosceles triangle, and the S valve 10 is swingable about the axis of the delivery line to a pair of defined operating positions, in each of which it is in register with the front of one of the cylinders and leaves the other in open communication with the interior of the feed chamber. It will be seen that the S valve must always be in register with the discharging cylinder (that is, the cylinder whose piston is moving forwardly), while the other cylinder is being charged from the feed chamber 6.

The S valve 10 is actuated in such swinging motion by hydraulic motor means here shown as comprising a pair of single acting reciprocating hydraulic actuators VA-l and VA-2, and it will be observed that the extension of actuator VA-l swings the S valve into register with cylinder C-ll, while extension of actuator VA-2 swings S valve into register with cylinder C-Z. The means by which the actuation of S valve 10 is coordinated with reciprocation of pistons P-1 and P-Z is described hereinafter.

Each of the pistons P-1 and P-Z is reciprocated by its own double-acting hydraulic driver or cylinder PA1 and PA2, the rod 12 of the hydraulic cylinder being rigidly attached to the piston in its associated pump cylinder. When pressure fluid is introduced through a port \13 in the rod or front end of the hydraulic cylinder PA-1 or PA2, the associated piston is moved rearwardly in its charging stroke, and when pressure fluid is introduced into another port 14 in the rear or head end of the hydraulic cyiinder, the piston is moved forwardly in its expulsion or discharge stroke. It will be appreciated that substantially more power must be exerted upon the pistons P-i and P-2 during their discharging strokes than during their charging strokes, and that the double-acting actuators or cylinders PA1 and PA2 are arranged with this in mind inasmuch as pressure fluid is applied to their smaller volume rod ends during the charging strokes of their associated pump pistons.

Referring now more particularly to FIGURE 3 hydraulic pressure fluid is supplied to the several actuators SM, VA-l, VA-2, PA-1 and PA-2 from hydraulic pump means, in this case shown as comprising three hydraulic pumps designated HP-l, HP-Z and HP-S. These pumps are of course connected with suitable drive means (not shown) such as an electric motor or a gasoline engine.

The pump HP-l is a constant delivery type and supplies pressure fiuid, through a duct 21 and a two-position control valve HCV-I, to the screw drive motor SM. The valve HCV?. is biased to, and normally maintained in, the position to drive the motor SM in its forward direction of rotation. However, if a stone or the like becomes wedged against the screw 8, obstructing its rotation, pressure in the duct 21 rises to the point at which a pressure responsive switch 22 in said duct is actuated, closing an energizing circuit (see FIGURE 4) to a solenoid 8-5 by which control valve HCV-l is shifted to its position in which it effects retrograde rotation of the screw drive motor SM. The screw turns in its reverse direction only momentarily, since the pressure switch opens as soon as pressure in duct 21 falls below the value at which pressure switch 22 is opened, breaking the energizing circuit to valve HCV1, and promptly thereafter the screw resumes rotation in its normal direction. The relatively brief period of retrograde screw rotation produced by this arrangement is usually adequate to clear a stone jam, and the mechanism just described, by reason of its fully automatic operation, eliminates the need for constant attendance upon the machine.

The other two hydraulic pumps HP-Z and HP3 provide pressure fluid for the pump piston actuators PA-1 and P2 and the S-valve actuators VA-l and VA2, and it will be observed as the description proceeds that those two pumps are so connected as to afford the utmost flexibility and efficiency in the utilization of available power.

Pump HP-Z is a variable delivery type, and its output is utilized to drive the pump pistons P-1 and P2 only in their forward discharging strokes. The output side of pump HP-Z is connected, by means of a duct 24, with the inlet of a hydraulic control valve HCV-D of the open center type which is biased to its neutral or inoperative position at which fliud entering its inlet is bypassed to a reservoir, but which can be actuated to its operative positions by means of a pair of solenoids S-E and S-F. When solenoid S-E is energized, it effects movement of control valve HCV-D to, and maintains it in, an operative position (shown in FIGURE 3) in which hydraulic actuator PA1 for piston P-l receives pressure fluid at its rear port 14, while return fluid vents from the rear port 14 of the actuator PA2 for piston P2. Similarly, when solenoid S-F is energized, piston F-Z is caused to move in its discharging stroke.

Because pump HP-2 is of the variable delivery type, the hydraulicjorce exerted upon the pump pistons P-1 and F2 in their discharging strokes can be matched to the viscosity of material being pumped, the length of the delivery line, and the height to which the material must be pumped, to obtain maximum pumping capacity for the power available.

Hydraulic pump HP-3 is of the constant delivery type, but a portion of its output is preferably diverted to the duct 24 through which pressure fluid is supplied to the discharge stroke sides of actuators PA-l and PA2. Thus, assuming that pumps HP2 and HP-3 are both piston type pumps, with ten cylinders each, the output of one cylinder of pump HP-3 is fed to duct 24, so that the paralleled outputs of pumps HP-Z and HP-3 are normally equivalent to that of an eleven cylinder pump. The output of three other cylinders of pump HP-3 is made available, through a duct 27 and a hydraulic control valve HCV-V, to the two single-acting hydraulic actuators VA-l and VA-2 which move the S-valve to and from its positions of register with the pump cylinders C1 and C-2. The output of the remaining six cylinders of pump HP-3 is normally made available to the front ports 13 of piston actuators PA-l and PA-2, by way of a duct 28 and a control valve HCV-C which is generally similar to valve HCV-D and which can be actuated to its operating positions by means of solenoids S-C and SD. When solenoid S-C is energized to hold valve HCV-C in the position shown, pressure fluid is brought to the actuator PA-2 for piston P-2, and when solenoid S-D is energized piston P-l is caused .to move in its charging stroke.

Through an adjustable flow divider 29 a greater or lesser portion of the output of a certain number of the cylinders of pump HP1 can be fed into the duct 28, for increasing the speed of the charging strokes of pistons P-1 and P-2, while the remainder of the output of said cylinders is vented. If the pistons move too fast in their charging strokes, even when all fluid from said cylinders of pump HP-l is vented through the flow divider 29, a portion of the output from three of the six cylinders of the pump HP-3 that are normally used for moving the pistons in their charging strokes can be vented through another flow divider 31.

It should be observed that an accumulator AC is connected with duct 27 leading to the inlet of control valve HCV-V, to be supplied with pressure fluid from pump HP-3 during the intervals when the S-valve 10 is maintained in one or the other of its operating positions by its actuators VA-l or VA-2. The pressure is retained in the accumulator during the time the control valve HCV-V is shifted through neutral to a new operating position due to the fact that this control valve is of the closed center type. Hence, as soon as the control valve has been actuated to a new operating position, the S-valve is shifted at high speed due to the sudden release of pressure fluid from the accumulator to the selected drive cylinder VA1 or VA-2. Excessive pressure in the duct 27 can, of course, be relieved through a relief valve RV-l.

The several hydraulic valve operating solenoids SA, S-B, SC, SD, S-E and SF are controlled by means of the electrical circuit illustrated in FIGURE 4, by which motions of the pistons P-1 and P-2 and of the S-valve 10 are coordinated and synchronized with one another. In general, this electrical circuit comprises front and rear double-pole limit switches for each cylinder (respectively designated I.S1F and LS-IR for piston P-1, and LS-ZF and LS-2R for piston P-Z), a pair of four terminal relays designated R-1 and R-2, a pair of six terminal relays designated R-3 and R4, a two position switch LS3 adjustably associated with the S-valve 19, and the solenoids just mentioned. In addition, the circuit can include certain manually actuatable momentarycontact pushbutton switches, as described hereinafter.

Each of the limit switches LS-lF, LS1R, LS2F and LS-2R associated with the pistons P-1 and P-2 has a normally open pair of terminals T-l and a normally closed pair of terminals T-2. The limit switches for each piston can be suitably mounted near the opposite ends of its actuator cylinders PA-l or PA-2, and they can be actuated by means of a pair of cam-like trip dogs that are mounted on a carrier 36 attached to its piston rod 12. Each of the trip dogs 35 is adjustable along its carrier in directions parallel to its piston axis to provide for establishment of the exact point along the piston strokes at which its associated limit switches will be actuated. Alternatively, the dogs 35 could be fixed on the rods 12 and the limit switches mounted for adjustment relative to the actuator cylinders lengthwise of the piston rods 12.

The four terminals of each of the relays R-1 and R-2 comprise a normally open pair of contacts T3 and a normally closed pair of contacts T-4. The six terminals of each of the relays R-3 and R-4 comprise two pairs of normally open contacts T5 and T-6 and one pair of normally closed contacts T7.

In the following description of the electrical circuit it will be assumed that pumps I-IP-l, HP-Z and HP-3 are running, that current is flowing in mains L-I and L-2 by which the electrical circuit is supplied, and that, as indicated by the positions of the pistons in the hydraulic actuators PA-l and PA2, piston P1 is partway through its discharging stroke while piston P-2 is partway through its charging stroke. This is the condition of the elements of the hydraulic system illustrated in FIGURE 3 and of the electrical system as shown in FIGURE 4.

In this situation relays R1 and R4 are energized, as explained hereinafter, relays R-2 and R-3 are deenergized, and solenoids SC and SE, which are connected in parallel, are likewise energized to hold their respective control valves HCV-C and HCV-D in the positions illustrated in the hydraulic diagram, FIGURE 3. The energizing circuit for solenoids SC and SE can be traced from main line L1 through switch LS-3, a conductor 41 connecting one terminal 42 of said switch with the now-bridged (but normally open) contacts T-5 of energized relay R-4, and thence through another condoctor 44 to the parallel connected solenoids S-C and SE.

Under the conditions described, solenoid SA is also energized so that it holds control valve HCVV in the position illustrated in FIGURE 3 in which pressure fluid is applied to charge the accumulator AC and to maintain actuator VA-l extended, with the S-valve 10 in register with pump cylinder C1. The energizing circuit for solenoid SA can be traced from line L-l by way of a conductor 46 to the now bridged (but normally open) contacts T3 of energized relay R-l, thence by way of a conductor 47 to normally closed terminals T-7 of relay R-3, and thence by way of a conductor 48 to solenoid SA.

The flow dividers 29 and 31 are so adjusted that the charging (rearwardly moving) piston (in this case P-2) reaches the end of its stroke slightly before the other piston reaches the end of its discharging or expulsion stroke, this being the desired condition.

In general, when rear limit switch LS-ZR is actuated it breaks a holding circuit for relay R-1, and the resulting opening of its terminals T3 causes de-energization of the solenoid SA, and the valve HCV-V thus returns to its neutral position. Substantially simultaneously, actuation of limit switch LS-ZR energizes relay R-2 to provide for energization of solenoid SB as soon as piston P1 reaches the end of its discharging stroke. Note that each of the relays R1 and R-2 is energized upon bridging of the normally open terminals T-l of a rear limit switch and is de-energized upon breaking of a holding circuit therefor leadingthrough the normally closed terminals T2 of the other rear limit switch.

When front limit switch LS-lF is actuated, solenoid R-4 is de-energized and solenoid R-3 is energized. Thus each of relays R-3 and R4 is energized upon bridging of the normally open terminals T-l of a front limit switch and is de-energized by interruption of its self-holding circuit through the normally closed terminals TZ of the other front limit switch. Each of the relays R-3 and R4 has normally open terminals T5 that control energization of the solenoids S-C, S-D, S-E, and S-F that govern motions of the pistons P-1 and P-2, hence de-energization of either of those relays effects termination of piston strokes. The energizing circuits for the piston controlling solenoids S-C, S-D, SE and S-F also includes the switch -31 that is actuated by the S-valve 10, and consequently the pistons do not begin to move in their new strokes until switch LS3 is thrown to a position in which it completes a circuit through terminals TS of whichever of relays R-3 or R- is then energized.

More specifically, starting from the conditions described above and illustrated in the diagrams, the relay R1 is energized and held in that condition through a self-holding circuit controlled by normally closed terminals T-2 of switch LS-ZR, and which circuit can be traced from line L-l, by way of the conductor 46 and the terminals T-3 of relay R-l, thence by way of conductor 47 to a conductor 49 through the normally closed terminals T2 of switch LS2R, and through a conductor 50 to the relay coil 51.

As piston P-2 nears the end of its charging stroke and the appropriate trip dog 35 actuates limit switch LS2R, the holding circuit for relay R-l is of course broken at terminals T2 of that switch. With de-energization of relay R1 and the return of its terminals T3 to their normally open condition, the previously described energizing circuit for solenoid S-A is also broken, whereupon valve HCV-V moves under bias to its neutral position, so that it is ready to effect a prompt shifting of S-valve 10.

Closure of the normally open terminals T1 of limit switch LS-ZR energizes relay R2, which in turn sets up an energizing circuit for solenoid S-B; but that solenoid is not actually energized until relay R-4 is ale-energized, as occurs (as explained hereafter) upon subsequent actuation of switch LS-IF. The energizing circuit for relay R-Z can be traced from line L-1 through conductor 46 to the now-bridged (but normally open) contacts T1 of limit switch LS-ZR thence by way of connected conductors 52 and 53 to normally closed terminals T2 of limit switch LS-IR, and thence by way of a conductor 54 to the coil 55 of relay R-2. Relay R2 maintains itself energized by means of a self-holding circuit controlled by terminals T2 of switch LS-IR, and which can be traced from line L-l through a conductor 56 and to now bridged (but normally open) terminals T3 of relay R-2, thence through a conductor 57 to conductor 52 in the previously described energizing circuit. The energizing circuit for solenoid S-B which is partially completed upon closure of relay R-2 can be traced from conductor 52, which connects with line L1 through now closed terminals T1 of LS-ZR, to normally closed (but now unbridged) terminals T7 of energized relay R-4, and thence, by way of a conductor 58 to solenoid SB. It will be apparent that completion of this circuit requires only the de-energization of relay R-4 to bridge its terminals T-7.

Very shortly after limit switch LS-2R has been actuated, piston P-l nears the end of its expulsion stroke and actuates limit switch LS-IF, whereupon the control valves HCV-C and HCV-D for the two piston actuators PA-l and PA-Z are shifted to their neutral positions, and the S-valve 10 begins to swing away from its position of register with cylinder C1. When limit switch LS-IF is tripped, relay R-4 is de-energized, breaking the energizing circuit to solenoids SC and S-E and thus terminating the piston strokes. The self-holding energizing circuit for solenoid R-4 that is controlled by limit switch LS-1F can be traced from line L-l by way of a conductor 5, to terminals T6 of relay R-4, thence by way of connected conductors 60 and 61 to normally closed terminals T4 of limit switch LS-lF, and thence by way of a conductor 62 to the coil 63 of relay R4. When relay R4 is de-energized by opening of its self-holding circuit at terminals T-Z of switch LS1F, terminals T-7 of that relay are of course bridged to complete the above described energizing circuit for solenoid 8-3 that had been set up by actuation of limit switch LS-ZR; and hence control valve HCV-V is immediately shifted to the position at which it causes actuator VA-Z to swing the S-valve 10 away from register with cylinder C1.

It will be observed that in the interval between actuation of limit switch LS2R, when control valve HCV-V is centered, and actuation of limit switch LS1F, by which solenoid SB is energized, pressure fluid directed to control valve HCV-V charges the accumulator AC, or if the accumulator is fully charged, exhausts through a relief valve RV-l.

De-energization of relay R-4 also breaks the previously described energizing circuit for solenoids S-C and S-E, controlled by terminals T-S of that relay, and thereupon control valves HCV-C and HCV-D go to their center or neutral positions in response to their bias, terminating the stroke of both pistons. The front limit switches LS-lF and LS-ZF are adjusted to be actuated very slightly before their respective pistons reach the forward ends of their discharging strokes, to accommodate the time required for solenoids SC, SD, 8-H. and S-F to shift the control valves HCVC and HCV-D to their neutral positions and to compensate for lag due to other inertias in the system.

Substantially simultaneously with the opening of normally closed terminals T-Z of limit switch LS-IF, the normally open terminals T1 thereof are bridged, thereby energizing relay R-3 so that solenoids 8-D and S-F can be energized as soon as switch LS-3 flips over. The energizing circuit for relay R-3 can be traced from L-l, by way of a conductor 64 to terminals T1 of limit switch LS-lF, thence by way of a conductor 65 to the now closed terminals T t of relay R-l (said relay having been tie-energized a moment previously, when limit switch LS-2R was actuated), thence by way of connected conductors 66 and 67 to normally closed terminals T-2 of limit switch LS2F, and thence by way of connected conductors 68 and 69 to the coil 70 of relay R3. Relay R3 is also in a self-holding circuit that can be traced from line L-l, by way of conductor 46 and a conductor 71 to now bridged terminals T6 of relay R-3, thence by way of conductor 67, the normally closed terminals T2 of limit switch LS-ZF, and the conductors 68 and 69 to the coil 70.

With relay R-3 energized to bridge its normally open terminals T-S, solenoids SD and S-F can be energized as soon as the S-valve 10 reaches a predetermined point in its swing from its position of register with cylinder C-l to its position of register with cylinder C-2. Until the valve reaches that point, the switch LS-3 which is associated with the S-valve remains in the position shown, but when it passes that point it throws the switch LS-3 from circuit making engagement with its terminal 42 to engagement with its terminal 43, completing an energizing circuit to solenoids 8-D and S-F that can be traced from said terminal 43, by way of a conductor 73 to nowbridged (normally open) contacts T-rS of relay R-3, and thence by way of a conductor 74 to said solenoids. With solenoid S-D energized, piston P1 is caused to move in its charging direction, and with solenoid S-F energized piston P-2 is caused to move in its discharging direction.

The switch LS-3 is actuated when the S-valve 10 is slightly past the midpoint in its swing. Allowing for the normal delay in the response of the valves HCV-C and HCV-D to completion of the energizing circuit for solenoids 5-D and S-F, the pistons P-1 and P-2 move through very small fractions of their new strokes during the final stages of movement of the S-valve into register with cylinder C-2. This overlap in valve and piston timing is advantageous in speeding up the overall cycle time of the machine, and accommodates itself to normal operating characteristics of the pump inasmuch as there is normally some slack in the material being pumped at the beginning of each stroke, and the S-valve does not cause substantial restriction of the front of a cylinder during the last few degrees of its motion into register therewith.

As piston P-l moves in its charging stroke and piston P-2 moves in its discharging stroke, relays R-2 and R-3 remain energized through their self holding circuits described above.

When piston P-l nears the end of its charging stroke it of course actuates limit switch LS1R, breaking the holding circuit for relay R-Z to de-energize that relay and concomitantly de-energizing solenoid -13 to center valve HCV-V. Shortly theretfter, when piston P-Z nears the end of its discharging stroke, it actuates limit switch LS-ZF, de-energizing relay R3 and consequently de-energizing solenoids SD and S-F, and energizing relay R-4 to set up an energizing circuit for solenoids SC and S-E that will be completed as soon as switch LS-3 is flipped back to engagement with its contact 42.

If for any reason a limit switch should fail, or if it is desired to operate the machine with shorter than normal strokes of its pistons, or to reverse piston motion in midstroke, the limit switches can be by-passed by means of momentary contact push-button switches. One of these switches has a normally closed component PB-IA so connected in conductor 69 as to de-energize relay R-3 when actuated and has a normally open component PB1B so connected with line L-l and conductor 62 that when actuated it effects energization of relay R-4, all regardless of the positions of the limit switches. Another push-button switch has corresponding normally closed and normally open components PB2A and PB-ZB which similarly effect de-energization of relay R-4- and substantially concurrent energization of relay R-S. Another push-button switch has a normally closed component PB3A in the conductor 48 to break the circuit to solenoid S-A when it is actuated, and has a normally open component PB 3B which, when actuated, connects line L1 with conductor 58 to energize solenoid S-B. Similarly, a push-button switch having a normally closed component PB4A and a normally open component PB4B provides for substantially simultaneous de-energization of solenoid SB and energization of solenoid S-A.

It will be apparent that the push-button switches can be employed to elfect an initial synchronization of the several hydraulic actuators or" the machine, when it is first started, and that thereafter, under normal conditions, the push-button switches will not be needed but will be available in case of an emergency.

From the foregoing description taken together with the accompanying drawings it will be apparent that this invention provides an automatic control system for a hydraulically actuated pump of the character described, which control system provides for the utmost flexibility in operation of the pump so as to insure that the power available to it is at all times utilized for achieving the greatest obtainable pumping capacity and maximum speed of the pumping cycle.

I claim:

1. A pump of the type having a pair of pump cylinders, the pistons of which are driven back and forth between defined limits in charging and discharging strokes by double acting hydraulic cylinders, one of said pistons moving in its charging stroke while the other moves in its discharging stroke, said pump also having pump valve means movable to a pair of operating positions at each of which the pump valve means provides for communication of the charging pump cylinder with a supply of material to be pumped and for communication of the discharging pump cylinder with a delivery line, and valve drive means for actuating the pump valve means, said pump being characterized by:

(a) a first control element associated with each hydraulic cylinder and actuated thereby as the piston in its associated pump cylinder completes its charging stroke;

(b) a second control element associated with each hydraulic cylinder and actuated thereby as the piston in its associated pump cylinder completes its discharging stroke;

(c) control means for the valve drive means;

(d) means providing an operative connection between said control means and each of said control elements whereby initiation of movement of the pump valve means from one to the other of its operating positions is effected in dependence upon actuation of one of each of said first and second control elements;

(e) a third control element associated with the valve drive means and arranged to be actuated thereby during movement of the pump valve means through a position intermediate its operating positions;

(f) hydraulic control valve means for the hydraulic cylinders, for controlling the direction of motion of the pump pistons; and

(g) means providing an operative connection between the third control element and said hydraulic control valve means whereby actuation of the third control element initiates movement of each piston in a new stroke.

2. In a pump of the type having a plurality of pump cylinders the pistons of which are reciprocated between defined limits by reciprocable hydraulic drivers in such timed relation as to produce charging of one pump cylinder simultaneously with discharging of another pump cylinder, there being control valve means for said drivers actuatable to effect reversal of piston travel in the pump cylinders:

(a) pump valve means movable to a plurality of adjacent operating positions to in turn provide for charging of each cylinder from a supply of material to be pumped while at the same time providing for discharging of material from another pump cylinder to a delivery line;

(b) drive means for shifting said pump valve means to said operating positions thereof;

(c) control instrumentalities, one for each cylinder adapted to be actuated in consequence of the piston therein reaching its discharging limit;

(d) means rendered operative by actuation of the control instrumentality of each cylinder to initiate operation of said valve drive means;

(e) and control means rendered operative by the valve drive means at a time when said pump valve means is moved thereby to a position intermediate two adjacent operating positions thereof for effecting actuation of the control valve means so that commencement of piston travel in a new direction can take place while the pump valve means is in the final portion of its motion from one operating position to another.

3. The pump of claim 4, wherein the pump comprises two pumping cylinders, and wherein the pump valve means is driven in opposite directions by its drive means between first and second operating positions to provide for charging of either pump cylinder and discharging of the other pump cylinder.

4. The pump of claim 3, further characterized by (a) second control instrumentalities, one for each cylinder, adapted to be actuated in consequence of the piston therein reaching its charging limit; and

(b) means providing an interconnection between the first designated control instrumentality for each cylinder and the second control instrumentality for the other cylinder whereby said means for initiating operation of the valve drive means is rendered operative in dependence upon actuation of one of each of said first designated and second control instrumentalities.

5. The pump of claim 4, wherein each of said control instrumentalities comprises a limit switch; wherein switch actuator means connected with the piston of each pump cylinder actuates its switch at a time when said piston reaches its discharge limit; and wherein said switches and their respective switch actuator means are mounted for adjustment relative to one another to provide for precise timing of switch actuation substantially at the instant the pistons reach their discharging limits.

6. The pump of claim 4, wherein said control means comprises a control member which is acted upon by a part constrained to move with said valve means, and wherein said control member and said part are relatively adjustable to enable said control means to be rendered operative by the valve means at different positions of the latter intermediate said two operating positions thereof.

7. In a concrete pump of the type having a feed chamber from which the pump cylinders are charged, a feed trough that discharges into the feed chamber, and a rotatable screw conveyor in said trough to propel concrete along the trough and into the feed chamber in consequence of rotation of the conveyor in one direction:

(a) a reversible motor drivingly connected with the conveyor;

(b) and control means for the motor operable to effect rotation of the conveyor thereby in either direction, said control means including a control element which normally provides for operation of the motor to drive the conveyor in said one direction, but which is sensitive to the load on the motor to momentarily effect reverse rotation thereof in the event the load on the mottor exceeds, a predetermined value.

8. The concrete pump of claim 8, wherein the conveyor is driven by a reversible fluid motor; wherein a control valve for the motor is shiftable from a normal position at which it effects operation of the motor to drive the conveyor in said one direction, to a motor reversing position at which it effects reverse rotation of the conveyor; and wherein the motor control element of the control means comprises a pressure sensitive instrumentality which is operated by rise in fluid pressure in the motor above said predetermined value to momentarily effect reversal of the motor.

9. In a pump for plastic material having a pair of pump cylinders, a pump piston reciprocable in each pump cylinder, a pair of double acting hydraulic cylinders, one for actuating each pump piston and each having a rod end into which pressure fluid can be introduced for driving the pump piston in a charging stroke and a head end into which pressure fluid can be introduced for driving the pump piston in a discharging stroke, and a pump valve actuatable by reversible hydraulic drive means for motion between a pair of operative positions in each of which a different one of the pump cylinders is communicated with a delivery line while the other is communicated with a supply of material to be pumped:

(a) first and second solenoid actuated control valves, each movable by solenoid energization to a pair of operative positions and to a solenoid deenergized open center position;

(b) means providing first and second pressure fluid sources;

(c) duct means by which the first control valve is operable to supply pressure fluid from the first pressure fluid source selectively to the head end of either hydraulic cylinder while simultaneously venting the head end of the other hydraulic cylinder;

(d) duct means by which the second control valve is operable to supply pressure fluid from the second pressure fluid source selectively to the rod end of either hydraulic cylinder while simultaneously venting the rod end of the other hydraulic cylinder;

(e) a third solenoid actuated control valve movable by solenoid energization to a pair of operative positions and to a solenoid deenergized neutral position;

(f) means providing a third pressure fluid source;

(g) duct means connecting the third control valve with the third pressure fluid source and with said hydrau lic drive means;

(h) discharging and charging limit switches associated with each pump piston and arranged for actuation when the pump piston approaches the ends of its strokes;

(i) means so connecting each of the charging limit switches with the third control valve as to effect solenoid deenergization thereof when a pump piston approaches the end of a charging stroke;

(j) means so connecting each of the discharging limit switches with the third control valve as to cause solenoid energization thereof whereby actuation of the pump valve is effected when a pump piston reaches the end of a discharging stroke;

(k) means so connecting each of the discharging limit switches with the first and second control valves as to effect solenoid deenergized movement of the same to their open center positions when a pump piston reaches the end of a discharging stroke;

(1) a pump valve switch arranged to be actuated when the pump valve is moving through a position intermediate its operative positions; and

(m) means connecting the pump valve switch with the first and second control valves for effecting solenoid energized motion of the same to operative positions at which they permit flow of fluid to and from the ends of the hydraulic cylinders to cause the pump pistons to begin new strokes as the pump valve moves through said position intermediate its operating positions.

10. The pump of claim 9, further characterized by:

(a) the third pressure fluid source comprising an accumulator and fluid pump means; and

(b) the third control valve having a closed center neutral position whereby charging of said accumulator by the fluid pump means is effected when said third control valve is in its neutral position.

References Cited UNITED STATES PATENTS 3,068,806 12/1962 Sherrod 103-469 3,198,123 8/1965 Wilkinson et a1. 103-49 3,279,382 10/1966 Bennett 103-49 3,279,383 10/1966 Smith 10349 ROBERT M. WALKER, Primmy Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,380,388 April 30, 1968 Eugene L. Sherrod It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 49, "P-Z" should read PA Z Column 6,

line 1, "cylinders" should read cylinder Column 10, line 57, claim reference numeral "4" should read 2 Column 11, line 31, "mottor" should read motor line 32, claim reference numeral "8" should read 7 Signed and sealed this 16th day of September 1969.

(SEAL) Attest:

Edward M. Fletcher, Jr. WILLIAM E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents 

